NOTE: The nuget-packages currently does not support 64-bit. I'm sure it will be updated soon.
Create a new iOS project
Create a new solution and add an empty Universal iOS project.
Add the MonoGame nuget package
Right-click the iOS project and select Add -> Add Packages..
Search for MonoGame and select the first package that contains the project Templates.
Rereference the binaries
For some reason, the binaries isn't references correctly. If you build now it will not find any Xna/MonoGame related stuff.
Right-click the iOS project and select Edit References. Navigate back to the projects root folder and then down to Packages/MonoGame.Binaries.3.2.0/build/MonoTouch. Select both assemblies and click the Add button.
Delete the old startup stuff
Remove/delete AppDelegate.cs and Main.cs.
Build and run
The app will hopefully start up with the standard cornflower blue shade of nothingness.
All you have to do now is create a game and get rich!